Lyme disease or Lyme borreliosis is a vector-borne, multisystem inflammatory bacterial illness transmitted to humans by the bite of ticks (Ixodes species) carrying spirochetes of the genius Borrelia. The disease presentation varies widely, and may include rash and flu-like symptoms in its initial stage, and musculoskeletal, arthritic, neurologic, psychiatric and cardiac manifestations in later stages.
Lyme disease is clinically manifested in three phases as:                early localized disease with skin inflammation,        early disseminated disease (such as heart and nervous system involvement, including palsies and meningitis)        late disseminated disease (such as motor and sensory nerve damage and brain inflammation and arthritis).        
Due to the difficulty in culturing the Borrelia spirochetes in the laboratory, diagnosis of Lyme disease is typically based on the clinical examination findings and a history of exposure to endemic Lyme areas. The laboratory tests most widely used are serological tests based on an Enzyme-linked immunosorbent assay (ELISA) test detecting antibodies to Borrelia species, mostly B. burgdorferi, B. garinii and B. afzelii (see for example WO 94/19697). This method is unfortunately characterized by a poor sensitivity and specificity, which sometimes provides false-positive results, and very often is not able to diagnose infected patients. Therefore, humoral immunological tests based on antibody detection are not a reliable basis for diagnosis of Lyme disease.
Western blot test may also be used to confirm positive results from an ELISA. The Western blot detects antibodies to several proteins of Borrelia species.
It is also possible to detect bacterial DNA in fluid drawn from an infected joint or other body sites using Polymerase chain reaction (PCR). This method is used for people who may have chronic Lyme arthritis. It may also be used to detect persistent infection in the cerebrospinal fluid of people who have nervous system symptoms. However, the sensitivity of PCR techniques is also low.
If diagnosed in the early stages, the disease can be cured with antibiotics. If left untreated, complications involving joints, the heart, and the nervous system can occur. It is therefore crucial to be able to specifically detect/diagnose Lyme disease in an early stage in order to avoid complications that may develop in later stages.
The significant disadvantages (poor sensitivity and specificity) of humoral immunity tests (ELISA and Western-blot) and PCR lead to a significant medical need for better diagnostic tests for diagnosing Lyme disease.